This is simple, but it works so very well. If you use real Parmesan cheese, like Parmigiano-Reggiano, save those rock-hard rinds. They are magic flavor bombs. All you do is add them to soup or bean dishes. Add them at the start of cooking, because they need a good long while to soften up and release their flavor goodness.
They don’t make the dish taste cheesy, but rather add that elusive umami (rich, savory) character to the dish. I think it would be redundant to use the rind if you are already using meat or bacon fat or the like in your soup, but for vegetable-based dishes, it really adds a nice touch.
As to how much rind you should add, it’s kind of hard to say, since rinds vary in thickness. I don’t think it’s necessary to use a whole rind per pot–I usually break my rinds into two halves. The average chunk that goes in my pots is probably less than an inch high by maybe 3 inches long. It doesn’t really matter how much you use. Even a little will help, and there’s no such thing as too much.
I also like to eat chewy, softened rind when the cooking is done, and consider finding it a treasure hunt. Erik doesn’t understand the obsession–and I don’t want him to, because I want it all to myself.
I suspect other hard cheese rinds would work as well, but I haven’t tried it, because the Reggiano is such a staple around here, we can’t afford other hard cheeses!